Mould is tricky to get rid of. Try the suggestions above. Don't use any of the domestic bathroom "Mould killer" products - they all contain bleach and will make a mess of your sail!

There are also professional sail washing businesses about - one of these may be able to get rid of it but I suspect the idea of washing a Hobie kayak sail alongside the normal sails these guys clean would cause a few sniggers! Also I do not know how well the Hobie sail's window would stand up to the washing process.

The usual cause of mould is storing the sail damp or with sea salt still on it - if damp the mould grows in the damp spots - if salty, the salt is hydrophilic i.e. it attracts moisture from the air, so even if it was dry when you put it away, if the air around the sail becomes moist, the salt will attract that moisture onto the sail and cause droplets to form which, again, can allow mould to form - N.B. cold air is usually dry - warm air tends to be damp so if your storage location is cold you may find that mould is less of a problem. So, once you have got it clean again (if you can), don't put it away damp or store it for a long time after using it in salty water.

Mould is tricky to get rid of. Try the suggestions above. Don't use any of the domestic bathroom "Mould killer" products - they all contain bleach and will make a mess of your sail!

There are also professional sail washing businesses about - one of these may be able to get rid of it but I suspect the idea of washing a Hobie kayak sail alongside the normal sails these guys clean would cause a few sniggers! Also I do not know how well the Hobie sail's window would stand up to the washing process.

The usual cause of mould is storing the sail damp or with sea salt still on it - if damp the mould grows in the damp spots - if salty, the salt is hydrophilic i.e. it attracts moisture from the air, so even if it was dry when you put it away, if the air around the sail becomes moist, the salt will attract that moisture onto the sail and cause droplets to form which, again, can allow mould to form - N.B. cold air is usually dry - warm air tends to be damp so if your storage location is cold you may find that mould is less of a problem. So, once you have got it clean again (if you can), don't put it away damp or store it for a long time after using it in salty water.

It probably had salt on it which caused the mold because I wouldn't intentionally store anything wet. Thank you for the awesome advice. Thinking of it, I wonder if I can beef up my mast by putting a thin piece of wood in the center?

A question about beefing up your mast really befits a different thread from one about mould on a sail but here goes anyway:

The standard mast does flex quite a bit and, while I have never personally broken a mast, it is not hard to believe that it might well break if used in very strong winds.

However:1. it is not likely to be used in these conditions because it just gets too uncomfortable and the risk of a gust ditching you into the water increases so most people (i.e. me) will prefer not to sail in too high a wind2. when a sailboat leans to the wind the sail spills wind thus reducing the stresses on the mast - clearly a sailboat equipped with outriggers has less of a tendency to lean to the wind though it can still do so in which case the outriggers will submerge as the lean increases.3. as the mast deforms the sail shape also deforms and should spill wind thus reducing pressure on the mast.

So if you are going out in strong winds, using your weight as balance to counteract the tendency of the boat to lean in strong winds and especially if your boat is equipped with outriggers you can expect to see quite a lot of bend in your mast.

IMO putting a bit of wood up the middle of the mast tube is not likely to do a lot in terms of mast rigidity - engineering principles state that the rigidity of a tube will be much the same as the rigidity of a solid rod because most of the rigidity derives from the outer part of the rod, not the centre so beefing up the centre will not have a whole lot of effect. But there are four possible solutions to this that I KNOW will deliver less mast bend:a) don't go out in winds that are too strong b) don't use outriggers c) devise a roller reefing system so that some of the sail can be rolled away in stronger wind conditions d) stay the mast to prevent it from bending

I use a,b and c on a regular basis. As to d) some time ago I devised a system of stays for the mast which are very effective indeed at preventing mast bend, maintaining sail shape (and efficiency) and allowing you to add more sail for lighter winds/greater speed in the right conditions. My stays are made of very light spectra line and were a very cheap addition that allowed me to use a jib as well as the mainsail. As I say, they really worked wonders for sail shape & efficiency but they add a lot of complexity to the rig and you need to be very methodical when using them. I haven't used them for a couple of years.

Neat bleach is pretty caustic stuff & there ain't no way I'll ever be washing my sails in it no matter how weak a solution... the reason is that while I may not be able to detect any damage/ill effects as a result of using a weak beach solution, every time you use it you will inevitably be doing some damage, degrading the material and reducing the working life of the sail.

Each to their own but personally I'd rather put up with a few spots of mould.

I bent the mast on my Revo, just above the tube that holds it, while sailing in very strong winds. I was able to straighten it back out and then I shaved down an oak dowel and inserted it in the bottom of the mast. I can't remember the dowel length but I think it was the standard 36". The mast has stayed straight for many years now even though I've been sailing in many high wind conditions [always with Amas deployed]. I do roller reef some [by hand] when the white caps get big. Hobie did not consider it a warranty issue as I was admittedly out in winds stronger than they rate it for.....but that's when the sailing can be the most fun!

Not sure what type mast we're talking about. In terms of the AI and TI mast, there are only two sounds ways to stiffen the mast - increase the diameter which would require a major change to the boat and mast support pieces, or keep the same diameter and move to a higher modulus material. Okay, a third way is to increase the current wall thickness, but for the additional weight involved you don't get the same kind of stiffness increase you'd get with a larger diameter and/or a high modulus material.

What you don't want to do is start sticking stuff into or over the mast. Certain things need to happen when it flexes and inhibiting those things with outside influences can cause failure.